Statistical scares

The diagram in the article about a test to identify tumours that have the ability to spread is captioned "Chances of cancer recurring after having a prostate cancer removed %" and shows a red line that increases stepwise to 60 per cent over 50 months (14 December, p 19).

This is obviously wrong as the chances quickly sum to more than 100 per cent. It should probably have read "Chances of cancer having recurred after having a prostate cancer removed %".

This is particularly distressing to cancer patients as it implies, for example, that having survived for four years after surgery with no evidence of disease, a patient with the relevant tumour type has a 60 per cent chance of a recurrence. This is clearly not true. While the number of recurrences rises with time, the individual's risk must eventually fall.

As a regular contributor to an Internet cancer ...

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